This application is based on and claims priority from Japanese Application No. Hei. 2-98538 and Japanese Application No. Hei. 2-98539, both filed Apr. 13, 1990, the disclosures of both being incorporated by reference herein.
The invention relates to track judgment in an apparatus suitable for use in reproducing, e.g., magnetic recording disks.
Electronic still video cameras can record not only video signals, but if necessary can also record audio signals on video floppy disks. FIG. 1 is a block diagram showing the construction of one example of pertinent portions of conventional playback circuitry for such magnetic recording disks. A signal reproduced from a head 1 is amplified by a reproducing (playback) amplifier 2 and then applied to a high-pass filter and equalizer 3, a low-pass filter 4, and a band-pass filter 5.
The high-pass filter and equalizer 3 separates a high-frequency component from an input signal and equalizes and outputs the separated high-frequency component to a luminance signal demodulating circuit 6. The luminance signal demodulating circuit 6 demodulates the frequency modulated luminance input signal and outputs the demodulated signal to a luminance signal processing circuit 10 and to an audio signal processing circuit 9. The luminance signal processing circuit 10 processes the demodulated luminance signal Y and outputs the processed luminance signal to an adder 13. The audio signal processing circuit 9 processes the demodulated audio signal and outputs the processed signal as an AUDIO OUT signal through a switch 14.
In addition, the audio signal incorporates a flag indicating start or end, and various control codes. When such flag and control codes are detected at the audio signal processing circuit 9, the detection result is applied to a CPU 12.
The low-pass filter 4 separates a low-frequency component (an FM color signal component) from an input signal and outputs the separated component to a color signal demodulating circuit 7. The color signal demodulating circuit 7 demodulates the FM color signal and outputs the demodulated signal to a color signal processing circuit 11. The color signal processing circuit 11 processes the demodulated color signal and outputs the processed signal C to an adder 13.
The band-pass filter 5 separates a predetermined frequency band signal (an ID signal) and outputs the separated signal to an ID demodulating circuit 8. The ID demodulating circuit 8 demodulates the ID signal and outputs the demodulated signal to the CPU 12. The CPU 12 generates a character signal or the like corresponding to the ID signal whenever necessary, and applies the generated output to the adder 13. The ID signal includes informations as to the track number, a recording date for the video signal and the like.
The adder 13 adds up video signals from the luminance signal processing circuit 10, the color signal processing circuit 11, and the CPU 12, and applies the sum as a VIDEO OUT signal through the switch 14.
In the meantime, the CPU 12 judges whether the track being reproduced is a track on which a video signal is recorded or a track on which an audio signal is recorded, in accordance with a flow chart shown in FIG. 7 and then controls the switch 14. Specifically, during reproduction of a magnetic recording disk (not shown) by the head 1 (Step S1), the CPU 12 judges whether or not an ID is present or not in the output of the ID signal demodulating circuit 8 (Step S2). Since the ID (DPSK) signal is recorded on a track on which a video signal is recorded (hereafter a "video track"), the detection of the ID means that the reproduced track is a video track. Thus, when the reproduced track is a video track, the CPU 12 opens an upper contact of the switch 14 shown in FIG. 6 to mute the voice output (Step S4).
On the other hand, when the reproduced track is an audio track, a flag or control code is recorded on the audio track. Thus, when no ID signal is detected at Step S2 and the flag or control code has been detected at Step S3, the reproduced track is an audio track. As a result, the CPU 12 opens a lower contact (opposite to the contact in Step S4) of the switch 14 shown in FIG. 6 to mute the video signal (Step S5).
In this manner, the type of reproduced signal is selected and outputted correctly and automatically, irrespective of whether the reproduced track is video or audio.
The conventional apparatus judges the type of track, either video or audio, from the presence of the flag or control code incorporated in the audio track or the presence of the ID signal incorporated in the video track. As a result, judgment of the type of reproduced track may be subject to errors when errors occur during a data reading operation. In addition, the conventional apparatus must be provided with the audio signal processing circuit and the ID signal demodulating circuit. An output which is produced from either the audio signal processing circuit or the ID signal demodulating circuit has to be used to judge the type of the track, and thus the conventional apparatus is disadvantageous in that a relatively long period of processing time may be required.